Question

The radius of an iron rod is decreased to one fourth of its original radius. If its volume remains constant, then the length will become.

• A. 2 times
• B. 12 times
• C. 8 times
• D. 16 times

Answer 1

The correct option is D 16 times

Solution:- Volume of original rod =$\pi r^2$h
Changed volume of changed rod = $\pi {\left(\frac{r}{4}\right)}^2{h}_1$
But, Volume remains constant.
$\pi r^2$h = $\pi {\left(\frac{r}{4}\right)}^2{h}_1\Rightarrow h_1$ = 16h

Option(d).